Implantable medical sensors and related methods of use

ABSTRACT

According to one aspect, an implantable medical device may include an anchor assembly configured to anchor the medical device to a body lumen. The implantable medical device may also include a capsule. The capsule may include a pH sensor. The pH sensor may be configured to measure a pH of contents within the body lumen. The capsule may also include a power source, a controller, and an impedance sensor. The impedance sensor may be configured to measure an impedance within the body lumen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalApplication No. 62/594,705, filed on Dec. 5, 2017, which is incorporatedby reference herein in its entirety.

TECHNICAL FIELD

Implementations of the present disclosure relate to devices and methodsfor measuring one or more of pH, position, and impedance with animplantable medical device. More specifically, at least some embodimentsof the present disclosure relate to devices and methods for diagnosinggastroesophageal reflux disease (GERD) or other abnormalities orailments in the gastrointestinal tract.

BACKGROUND

GERD is a condition associated with the gastrointestinal tract system.GERD is a condition in which stomach contents leak backwards from thestomach into the esophagus through the lower esophageal sphincter (LES).The leak may be caused by a weak LES or excess gastric pressure. Theleaked contents may irritate the esophagus. The irritation may causeheartburn and other symptoms.

Devices for GERD diagnosis should be able to differentiate betweendigestion events like swallowing, stomach contraction, and vomiting.However, current GERD diagnosis devices may be imprecise in the way theydifferentiate between digestion events. As such, the devices may notoperate in the manner desired when a digestion event takes place.Furthermore, current systems to diagnose GERD are limited in the numberof sensors included, the accuracy of the system, and the limitedmonitoring time in which the system is effective.

Currently, pH probes are used as a standard diagnostic tool to detectGERD, however most pH probes don't have sensors that indicatedirectionality of the reflux event, which may result in false negativediagnoses. Also, implantable wireless pH monitoring to diagnose GERD iscurrently susceptible to false negative results.

The medical devices and methods described herein are provided to rectifydeficiencies described in conventional diagnostic sensors and offerimprovements that may help address other problems.

SUMMARY

Embodiments of the present disclosure relate to, among other things,medical devices for measuring pH, impedance, and/or position of apatient. Each of the embodiments disclosed herein may include one ormore of the features described in connection with any of the otherdisclosed embodiments.

According to one aspect, an implantable medical device may include ananchor assembly configured to anchor the medical device to a body lumen.The implantable medical device may also include a capsule. The capsulemay include a pH sensor. The pH sensor may be configured to measure a pHof contents within the body lumen. The capsule may also include a powersource, a controller, and an impedance sensor. The impedance sensor maybe configured to measure an impedance within the body lumen.

In other aspects of the present disclosure, the implantable medicaldevice may include one or more of the features below. The anchorassembly may be configured to release from a wall of a body lumen within1-7 days. The anchor assembly may be configured to couple the medicaldevice to a wall of an esophagus. The controller may include atransmitter. The transmitter may be configured to transmit a signal to areceiver located outside of the body lumen. The capsule may be anelongated cylindrical structure forming a helix. The impedance sensormay be configured to sense a direction of travel of contents within thebody lumen. The implantable medical device may be in electricalcommunication with a data acquisition module. The capsule may furthercomprise a position sensor. The anchoring assembly may include a firststructure at a distal portion of the capsule and a second structure at aproximal portion of the capsule. Each of the first structure and thesecond structure may be configured to anchor the medical device to thebody lumen. The anchoring assembly may include a bioabsorbable portion.The implantable medical device may include an optical assemblyconfigured to visualize an area within the body lumen,

In other aspects, a method for sensing within a body lumen of a patientmay include sensing a pH with an implanted medical device coupled to thebody lumen. The method may also include sensing a direction of travel ofcontents within the body lumen with an impedance sensor of the medicaldevice. The method may also include determining, based on the sensed pHand the sensed direction of travel, whether the patient has experiencedan event. The method may further include transmitting data from theimplanted medical device to a data acquisition module located outside ofthe body of the patient.

In other aspects of the present disclosure, the method for sensingwithin a body lumen of a patient may further include one or more of thefeatures below. The method may include sensing a position of a medicaldevice within the body lumen. The method may also include wirelesslytransmitting a sensed pH and a sensed direction of travel to a dataacquisition module. The method may include determining whether thesensed pH is less than 4 when determining whether the patient hasexperienced an event. The method may include releasing the medicaldevice from the body lumen after a period of 1-7 days. Also, the methodmay include determining whether the sensed direction of travel ofcontents is upstream when determining whether the patient hasexperienced an event.

In other aspects of the present disclosure, a method for sensing withina body lumen of a patient may include sensing a direction of travel ofcontents within the body lumen with an impedance sensor of the medicaldevice. The impedance sensor may be exposed to an interior of the bodylumen. The method may also include determining whether the patient hasexperienced an event based on the sensed direction of travel. The methodmay further include transmitting data from the implanted medical deviceto a data acquisition module located outside of a body of the patientwhen an upstream direction of travel is sensed.

In other aspects of the present disclosure, the method for sensingwithin a body lumen of a patient may further include one or more of thefeatures below. The method may also include sensing a position of thepatient with the implanted medical device, and then determining whethera patient has experienced an event is further based on the sensedposition. Also, the method may include releasing the implanted medicaldevice from a wall of the body lumen after 2-7 days.

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as claimed. As used herein, the terms “comprises,”“comprising,” or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not necessarily includeonly those elements, but may include other elements not expressly listedor inherent to such process, method, article, or apparatus. The term“exemplary” is used in the sense of “example, ” rather than “ideal.”

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated in and constitute a part ofthis specification. These drawings illustrate aspects of the presentdisclosure that, together with the written descriptions herein, serve toexplain this disclosure as follows:

FIG. 1 illustrates a perspective view of a medical device according toaspects of the present disclosure.

FIG. 2 illustrates a perspective view of a medical device according toaspects of the present disclosure,

FIG. 3 illustrates a block diagram of an exemplary method of using themedical devices disclosed herein according to aspects of the presentdisclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. The term“distal” refers to the end farthest away from a user when introducing adevice into a patient. The term “proximal” refers to the end closest tothe user when placing the device into the patient. The term “downstream”refers to the direction of flow of a substance through thegastrointestinal tract when ingested through the mouth of a patientrunning from the mouth through the esophagus to the stomach. The term“upstream” refers to the direction of flow of a substance from thestomach through the esophagus towards the mouth of a patient. The term“reflux event” includes a digestive event in which stomach contents orother substances leak backwards from the stomach, in an upstreamdirection, into the esophagus through the lower esophageal sphincter(LES). When used herein, the terms “approximately” and “substantially”may indicate a range of values within +/−5% of a stated value.

The present disclosure is drawn to implantable medical devices formeasuring one or more of pH, impedance, position, and other parametersof a patient's body, and related methods. In general, embodiments of themedical devices may include a pH sensor, a position sensor, and animpedance sensor. The medical devices may be implantable into a bodylumen of a patient, such as the esophagus. In some examples, the medicaldevices may include an attachment means for attaching the medical deviceto the esophageal wall.

In exemplary embodiments of the present disclosure, GERD diagnosis andtreatment may be performed using a medical device including one or moresensors or sensor assemblies, a controller, and a data acquisitionmodule. The diagnosis is initiated by implanting the medical device intoa patient and monitoring one or more locations along the esophagus usingthe one or more sensors. The sensors generate input signals indicativeof sensed pH, impedance, position, or other suitable parameters, at thelocation of the medical device. The controller receives the inputsignals and executes one or more algorithms used to determine whetherthe input signals are indicative of one or more digestive events. Adigestive event may be a reflux event, a patient swallowing food ordrink, or other digestive activity within the gastrointestinal tract.Based on the determination, the controller may transmit sensor data toone or more data acquisition modules. Though this description describesdiagnostic devices for GERD, embodiments of the present disclosure maydiagnose and/or treat other ailments throughout the body.

Referring to FIG. 1, a medical device 100 may include a proximal anchor104 and a distal capsule 102. Capsule 102 may have a rectangular shapeand may have a distal section 122 and a proximal section 124. Anchor 104may be coupled to the proximal section 124 of the capsule 102. Asexplained in further detail below, one or more sensors may be coupled tocapsule 102 for measuring pH, impedance, position, posture, fluid orother substance flow, or other parameters. Capsule 102 may include atleast one pH sensor 108 and may include at least two impedance sensors106, 110. In other examples, capsule 102 may include two, three, four,or more pH sensors 108 and/or may include one, three, four, or moreimpedance sensors 106, 110, In some examples, a pH sensor 108 may bepositioned on the capsule 102 between two impedance sensors 106, 108,one impedance sensor 106 located distal to the pH sensor 108 and oneimpedance sensor 110 located proximal to the pH sensor 108 (shown inFIG. 1). Capsule 102 may further include a position sensor 112, a powersource 114, and a controller 116. In some examples, capsule 102 mayinclude a plurality of motion sensors 112, power sources 114, and/orcontrollers 116. Capsule 102 may be wirelessly connected to a dataacquisition module 130, for example, wirelessly connected via atransmitter included in controller 116 present on or in capsule 102. Inother examples, a transmitter may be included in capsule 102 separatefrom controller 116. In some examples, capsule 102 or anchor 104 mayinclude an optical sensor, such as a camera. A camera may be used toassist in the placement of medical device 100 within a body lumen of apatient.

Capsule 102 may be any structure that can retain the desired sensors andelectrical components in the desired part of the anatomy. Capsule 102may be spherical, pyramidal, cylindrical, or any other shape. In someexamples, capsule 102 may be adapted to be received within a workingchannel of a delivery device, such as an endoscope or catheter. Capsule102 may provide a protective body covering one or more components (suchas battery, controller) and provide a fluid-tight seal preventingingress of fluids that could harm operation of medical device 100.Capsule 102 may be rigid or flexible, and may be made of any suitablebiocompatible material. In some examples, capsule 102 may be part of aself-powered micro-fuel cell. Capsule 102 may be made of a material thatwould enable bio-fuel cell production, such as a thin film metal layeror nano-carbon material. In some examples, capsule 102 or portions ofcapsule 102 may be a material to enable capacitive coupling, such as athin film or non-carbon material. In some examples, capsule 102 may be aflexible cylinder with a diameter less than or equal to 5 mm, includingfor example 4.2 mm. Capsule 102 may be designed to be implantedapproximately 3-5 cm above the lower esophageal sphincter (LES). In someexamples, medical device 100 may include multiple capsules eachcontaining separate components, such as a capsule for the pH sensor, acapsule for the control, etc.

Anchor 104 may be releasably coupled to capsule 102 and may have a shapeof a loop, or partial loop, enclosing an opening 105. Anchor 104 may bean anchor assembly and may include multiple components, such as a wireloop coupled to capsule 102 and a fastening means used to couple thewire loop to a patient, such as to the esophageal wall of a patient. Insome examples, anchor 104 may include a suture, a clip, a hook, anadhesive, a spike, a spiral wire, a spring, and/or a looped wire.Portions of anchor 4 may have different diameters than other portions.For example, a proximal portion of anchor 4 may have a larger diameterthan a distal portion of anchor 4. In some examples, multiple anchors104 may be coupled to different portions of capsule 102 and may bespaced apart from each other. In one example, a loop (e.g. of wire) maybe coupled to a proximal section 124 of capsule 102 and a second loopmay be coupled to a distal section 122 of capsule 102. In some examples,anchor 104 may encase capsule 102. The use of multiple anchors coupledto capsule 102, which may provide multiple anchoring points affixing thecapsule 102 to the esophageal wall or other body lumen, may assist inmaintaining directional orientation of the medical device 100 within abody lumen of the patient.

Anchor 104 may include an actuator for releasing the capsule 102 fromall or part of the anchor 104. In some examples, anchor 104 may includea grasper or clipping device, or may include an adhesive present on aportion of the surface area of capsule 102. In other examples, anchor104 may include a lever, button, slide, or switch, to provide amechanical, magnetic, and/or electrical release mechanism to release thecapsule 102 from the anchor 104, a portion of the anchor 104 or aportion of the anchor assembly. Releasing the capsule 102 from theanchor 104 may allow the capsule 102 to pass through thegastrointestinal tract of the patient to exit the patient's body. Insome examples, anchor 104 or a portion of anchor may be a bioabsorbablestructure which may deteriorate over a predetermined period of time,such as one, two, three, four, five, six, or seven days, two weeks, onemonth, or any other time period. For example, bioabsorbable suture maybe used to tie anchor 104 in FIG. 1, to the esophageal wall. The suturemay absorb over a predetermined time, releasing anchor 104 from thewall, allowing capsule 102 to travel through the digestive tract. Inother examples, a bioadhesive present on a portion of the surface areaof capsule may be configured to deteriorate and release capsule after aspecific period of time.

Once implanted in a patient, anchor 104 may be secured to a portion ofthe esophageal wall to help secure medical device 100. As describedfurther below, anchor 104 may be positioned in the esophagus or thegastro-esophageal junction (GEJ) region. In some examples, medicaldevice 100 does not include anchor 104. In some other examples, medicaldevice 100 may exert a radially outward force on a body lumen to securemedical device 100 to the inner wall of a body lumen for example,capsule may be ring-shaped with its radial outer surface contacting theinterior surface of the esophageal wall. The ring-shaped capsule may besufficiently rigid and have a sufficient diameter to anchor itself inthe esophageal lumen. The ring-shaped capsule may be sufficiently rigidIn other examples, medical device 100 may be secured directly to thepatient's tissue using sutures or any other suitable attachmentmechanism. In some examples, medical device 100 may have a long geometrywhereas the device length exceeds the diameter of the body lumen inwhich it is implanted. In some examples, medical device 100 may includean elongated capsule and a plurality of impedance and pH sensors insidethe elongated capsule, and may have a length (long dimension) greaterthan the actual width or diameter of the body lumen in which the medicaldevice is inserted.

pH sensor 108 may be used to monitor pH values of bodily fluids,including stomach fluids, and other substances within the body of thepatient. pH sensor 108 is coupled to capsule 102 so that sensor 108comes into contact with the bodily fluid to be monitored. In someexamples, pH sensor may be partially or fully exposed to contents withinthe gastrointestinal tract. pH monitoring using pH sensor 108 may beperformed continuously, intermittently, or upon the trigger of anothersensory input detector from another sensor included in or on capsule102, such as position sensor 112 or impedance sensor 106, 110. In someexamples, pH sensor 108 may include one or more sensors forming a pHsensor assembly. pH sensor 108 may be in electrical communication withany of the other components included in medical device 100, includingdata acquisition module 130 or any other sensors incorporated in medicaldevice 100.

Position sensor 112 may detect the position of the patient and/or theposition of the esophagus relative to the ground. Position sensor 112may include a posture sensor, an accelerometer, a gyroscopic sensor, a6-axis motion sensing device, a digital position sensor, or anycombination thereof. Position sensor 112 may detect whether the patientis standing or sitting upright, with the patients esophagus runningsubstantially perpendicular to the ground, or lying down, with thepatient's esophagus running substantially parallel to the ground. Insome examples, position sensor 112 may detect the position of capsule102 relative to the esophagus or other internal body lumen of thepatient. Position sensor 112 may be in electrical communication with anyof the other components included in medical device 100, including dataacquisition module 130 or any other sensors incorporated in medicaldevice 100.

Impedance sensors 106, 110 may be multichannel intraluminal impedance(MII) sensors or any other impedance sensors suitable to detect animpedance value therebetween and suitable for implantation in a humanbody. Impedance sensors 106, 110 may detect the intraesophageal bolustransport or directional flow activity within a body lumen of thepatient. In some examples, impedance sensors 106, 110 may measure animpedance value between each sensor 106, 110, or an impedance delta. Insome examples, medical device 100 may include one impedance sensor, orthree or more impedance sensors. When medical device 100 is implantedinto a body lumen of a patient, impedance sensors 106, 110 may detectwhen the body lumen is filled with a substance, such as a gas, liquid,or solid, and which direction the substance is flowing through the bodylumen, such as downstream or upstream. Impedance sensors 106, 110 maydistinguish between substances being swallowed by the patient and areflux event associated with GERD. Impedance sensors 106, 110 may bepositioned on or in capsule 102, and capsule 102 may be coupled to theesophageal wall of a patient in such a way to position impedance sensors106, 110 along a direction of travel of substances through theesophagus, along the longitudinal axis of the esophagus. When anchoringcapsule 102, impedance sensors 106, 110 may need to be positioned toexpose the sensors to the interior passageway of the esophagus and maynot be positioned against the esophageal wall. By detecting whether adigestive event includes substances traveling downstream or upstream thegastrointestinal system, impedance sensors 106, 110 may assist inavoiding false negative or false positive diagnostic results that mayresult from recording data during downstream flow activity, such as whenthe patient is eating food, as a reflux event associated with GERD.

The various sensors and components of medical device 100 may beconnected to power source 114 to supply power to the components. Powersource 114 may be a battery, such as an implantable battery orwirelessly rechargeable battery coupled to capsule 102 or anchor 104. Inother examples, power source 114 may include multiple batteries or oneor more batteries combined with another source of power. In someexamples, power source 114 may be a self-powered device such as aMicrobial Fuel Cell (MFC) with a grapheme anode, which may be powered bysaliva, a kinetic energy harvesting device, and/or a battery. Powersource 114 may be wirelessly charged by a device, such as a batterycharging device located outside of the patient's body.

Controller 116 may include a processor that is generally configured toaccept information from any of the sensors or electrical components ofmedical device 100, and process the information according to one or morealgorithms. The processor may be a digital integrated circuit processor,analog processor or any other suitable logic or control system thatcarries out control algorithms. In some examples, controller 116 may bean M0-M4 class ARM device, a flexible microcontroller, and/or anotherform of embedded processor. Controller 116 may record treatment ordiagnostic parameters, e.g., sensor data, so that the data may beaccessed for concurrent or subsequent analysis. Controller 116 mayinclude software that provides a user interface to components within thesystem. The software may enable a user (e.g., patient or clinician) toconfigure, monitor, and control operation of medical device 100. Asdescribed in further detail below, software may be configured toperiodically or continuously sample the sensors present on medicaldevice 100 and broadcast information to data acquisition module 130. Insome examples, controller 116 may be configured to broadcast informationonly when certain events occur, such as only when the pH sensor 108detects a pH below a certain threshold value, when impedance sensors106, 110 detect a certain impedance, or when position sensor 112 detectsa certain position or posture of the patient.

Controller 116 may include a transmitter capable of broadcasting awireless signal to data acquisition module 130. For example, controller116 may include an integrated radio for a transmitter such as a NORDICnRF52. In some examples, a transmitter included in controller 116 may bea 2.4 GHz transmitter operable with Bluetooth technology and/or capableof being paired to portable devices such as a smartphone or a tablet. Inother examples, a transmitter included in controller 116 may be aproprietary 433 MHz ultra high frequency (UHF) transmitter capable ofbeing uniquely paired with a receiver, such as a smartphone or smartwatch, the patient could wear.

Data Acquisition Module 130 may be any means for receiving datatransmitted wirelessly from medical device 100. In some examples, dataacquisition module 130 may be an application downloaded to a portabledevice, such as a smartphone or a tablet. In other examples, dataacquisition module 130 may include software downloaded to a computer orcontained within a portable electronic device worn by the patient, suchas a smart watch or other wearable electronic device. Data transmittedfrom medical device 100 may be stored and processed by data acquisitionmodule 130 for analysis by the patient or the patient's clinician. Insome examples, data acquisition module 130 may include a user interfaceby which the patient can input his or her symptoms during a digestiveevent, such as symptoms that occur while experiencing a reflux event.For example, the patient may input into the data acquisition module 130a symptomatic event description and record the time when the symptomaticevent occurred, the patient's body position, and/or food ingested priorto the event. Data Acquisition module 130 may provide input parameters,such as a symptomatic event description and time of event occurrence,within a software application present on the patient's smartphone,tablet, computer, or other electronic device.

FIG. 2 illustrates an additional example of a medical device 200 inaccordance with the present disclosure and similar to medical device 100discussed above. Medical device 200 includes capsule 202, anchor 204, pHsensor 208, impedance sensors 206, 210, position sensor 212, powersource 214, controller 216, and data acquisition module 230. The same orsimilar components of medical device 100 and medical device 200 may havethe same or similar characteristics as previously described inconnection with medical device 100. This discussion therefore will focuson the differences between devices 100, 200. Medical device 200 has anelongated cylindrical structure forming a helix or spring shape. In someexamples, medical device 200 may be designed to extend along and againstthe esophageal wall and may include a curvature that substantiallymatches with that of the esophageal wall of a patient. In otherexamples, medical device 200 may be flexible and/or may be biasedradially outward from the P-D (proximal-distal) axis (shown in FIG. 2)such that the radially outer surface is pressed against the esophagealwall when medical device 200 is implanted in the esophagus of a patient.Capsule 202 may have a contracted delivery state and an expandedimplantation state.

Another exemplary embodiment of a medical device in accordance with thepresent disclosure may includes a series of capsules each anchoredseparately within a body lumen of a patient. In such an embodiment, thesame or similar components of medical device 100 and medical device 200may be included in multiple different capsules and may have the same orsimilar characteristics as previously described in connection withmedical device 100. For example, a cluster of capsules may be coupled toa wall of a body lumen with a pH sensor in one capsule, a impedancesensor in another capsule, a position sensor in another capsule, etc. Inthis cluster configuration, each capsule may be in electroniccommunication with each other capsule in the cluster, and all of thecapsules may be in electronic communication with a data acquisitionmodule located outside of the patient.

Medical devices disclosed herein, such as medical devices 100 and 200,may be used in a variety of contexts. In one example, medical device 100may be used to diagnose GERD.

Medical devices disclosed herein may be delivered to a patient usingstandard delivery methods and devices. For example, medical device 100may be inserted into a delivery catheter and placed transorally into thepatient's gastrointestinal system. In some examples, medical device 100may be transported to a target esophageal site within the jaws of anendoscopic clipping device. The target esophageal site may be 2-5 cmfrom the lower esophageal sphincter. Coupling medical device 100 to theesophageal wall (or other portion of the GI tract) may include anchoringcapsule 102 with one or more anchors 104 such that the distal section122 is downstream from the proximal section 124 of medical device 100.For example, medical device 100 may be coupled to the esophageal wallwith an anchor assembly including a first anchor in the proximal section124 of medical device 100 and a second anchor in the distal section 122of medical device 100 such that the first anchor is upstream from thesecond anchor. Anchor 104, or multiple anchors if used, may be coupledto the esophageal wall of the patient to position medical device so thatimpedance sensors 106, 110 may detect the directional flow of substancesthrough the esophagus.

After implantation, medical device 100 may detect digestive events, suchas reflux of stomach contents, and wirelessly transmit sensor data, suchas data from pH sensor 108, position sensor 112, and impedance sensors106, 110 to data acquisition module 130. In some examples, data may betemporarily stored on medical device 100, such as in a memory ofcontroller 116, prior to transmission to data acquisition module 130.

After collection of data using data acquisition module 130, an anchorassembly may be configured to release the medical device from a bodylumen of the patient, such as the esophageal wall. The anchor assemblymay be configured to release after a specific or otherwise predeterminedtime period. In some examples, the anchor assembly may be configured torelease after one, two, three, four, five, six, or seven days, twoweeks, or one month. In other examples, the implanted medical device maybe removed by a clinician using standard removal methods. For example,medical device 100 may be pulled transorally from the patient.

Controller 116 may be configured to execute specific algorithms todetermine whether (or when) to transmit and/or record a digestive event.Controller 116 may be configured to aggregate sensor data from any ofthe sensors present on medical device 100, such as pH sensor 108,position sensor 112, and impedance sensors 106, 110. FIG. 3 illustratesan example of a “broadcast on event” monitoring algorithm 300 that maybe included in controller 116 and may require specific sensor datavalues to transmit digestive event data to data acquisition module 130.“Broadcast on event” may mean controller 116 is configured to transmitdata to data acquisition module 130 when certain sensor data valuethresholds are met or exceeded.

In FIG. 3, step 302 includes beginning digestive event monitoring, whichmay be initiated at the time medical device 100 is implanted into apatient, such as by manually pressing a button or powering on thedevice, or may be initiated after implantation, such as wirelesslyinitiated using data acquisition module 130. Step 304 includes readingposition sensor data to determine the posture of the patient, e.g.whether the patient is upright or lying down. In step 306, algorithm 300determines whether impedance sensors 106, 110 indicate upstream movementof a substance flowing through the esophagus, which would indicate areflux event is occurring. For example, impedance sensors 106, 110 maydetermine an impedance delta between two impedance sensors that mayindicate a particular direction of substance movement through theesophagus. By reading an impedance delta from the impedance sensors 106,110, the controller 116 may determine whether the digestive eventincludes substances traveling upstream or downstream the esophagus. If,after step 306, data from the impedance sensors 106, 110 indicates asubstance is moving downstream in the esophagus, controller 116 mayreturn to step 302 to continue event monitoring, without recording theevent since downstream movement most likely indicates the patient iseating or drinking and not having a reflux event. If, after step 306,data from the impedance sensors 106, 110 indicates a substance is movingupstream in the esophagus, then the controller 116 may proceed to step308 and may collect a pH sensor's data and/or determine whether anadaptive threshold has been met.

While FIG. 3 indicates that only sensor data with a pH of less than 4will move to step 310 of algorithm 300, the pH threshold level to moveto step 310 may be any adaptive threshold. The adaptive threshold may beset and periodically changed by a patient's doctor, may be stored on thedevice, and may depend on the level of severity of the patient'sillness. The adaptive threshold may be set based on the existence and/orseverity of the patient's GERD or other conditions such as Non-erosiveReflux Disease (NERD), hypersensitive esophagus, whether the patient isreceiving proton pump inhibitors (PPIs), among others. In some examples,the adaptive threshold may be set to a threshold pH of 4 or less (asshown in step 310 of FIG. 3) when a patient has mild to moderate GERD,for example when the patient has a Los Angeles GERD Grade Classificationof A or B. In other examples, the adaptive threshold may be set to athreshold pH of 6 or less when a patient has moderate to severe GERD,for example when the patient has a Los Angeles GERD Grade Classificationof C or D. In other examples, the adaptive threshold may be set to athreshold pH of 5 or less when a patient has NERD, hypersensitiveesophagus, whether the patient is receiving PPIs, or has other relatedconditions.

If the medical device 100 determines the adaptive threshold has not beenmet, shown in FIG. 3 as determining the pH level is not below 4, thenthe algorithm 300 may record the event as a non-acidic reflux event andmove back to step 302 to continue event monitoring. If the device 100determines the adaptive threshold is met or exceeded in step 308 (shownin FIG. 3 as determining whether the pH reading from the pH sensor 108is lower than 4), algorithm 300 will move to step 310 and monitor thedata from the sensors for a duration of time X, where X may be amonitoring time and may be any period of time such as 5 seconds. Thepatient's doctor may set the monitoring time X for step 310 and the timemay be 1, 2, 3, 4, 5, 6, 7, 10, or 15 seconds, or any other amount oftime. In step 310, if the adaptive threshold (shown in FIG. 3 as ph<4 instep 310) is met or exceeded for the entire monitoring time X, thealgorithm 300 may proceed to step 312 and transmit to a receiver (suchas data acquisition module 130, 230) an alert of a GERD event. If theadaptive threshold is not met or exceeded for the entire monitoring timeX in step 310, algorithm 300 my record a “peak detection only” event andproceed to step 306 of determining whether the impedance sensorindicates upstream movement. In some examples, if the adaptive thresholdis not met or exceeded for the entire monitoring time X in step 310,algorithm 300 may move back to step 302 and continue event monitoring.

After transmission of data received by the sensors of the medical deviceto a receiver, such as in step 312 of algorithm 300, the controller 116may return to step 302 and continue digestion event monitoring.Algorithm 300 is an exemplary algorithm, and any sensor threshold valuerequirements and/or adaptive threshold value requirements may be addedor interchanged with the requirements of algorithm 300.

By utilizing an algorithm such as algorithm 300 to determine when torecord digestive events while testing a patient for GERD, the frequencyof false positive and false negative testing may be mitigated. Forexample, by utilizing multiple different sensors for position, pH, andimpedance in an implantable device to collect patient data over a longerperiod of time than conventional diagnostic medical devices, cliniciansmay have more accurate and reliable diagnosis of GERD in patients.Similarly, utilizing a monitoring time, such as step 310 in algorithm300, may mitigate the number of false positive reflux events detected bythe sensors. Algorithm 300 utilized in the medical devices discussherein above provides a means to filter digestive events and only recordevents that include sensor data aligning with a reflux event.

While principles of the present disclosure are described herein withreference to illustrative embodiments for particular applications, itshould be understood that the disclosure is not limited thereto. Thosehaving ordinary skill in the art and access to the teachings providedherein will recognize additional modifications, applications,embodiments, and substitution of equivalents all fall within the scopeof the embodiments described herein. Accordingly, the invention is notto be considered as limited by the foregoing description.

1-20. (canceled)
 21. A method for sensing within a body lumen of apatient, comprising: sensing a pH with an implanted medical devicecoupled to the body lumen; sensing a direction of travel of contentswithin the body lumen with an impedance sensor of the medical device;based on the sensed pH and the sensed direction of travel, determiningwhether the patient has experienced an event; and transmitting data fromthe implanted medical device to a data acquisition module locatedoutside of a body of the patient.
 22. The method of claim 21, furthercomprising sensing a position of the medical device within the bodylumen.
 23. The method of claim 21, further comprising wirelesslytransmitting the sensed pH and the sensed direction of travel to thedata acquisition module.
 24. The method of claim 21, wherein determiningwhether the patient has experienced an event includes determiningwhether the sensed pH is less than 4 for a period of 5 or more seconds.25. The method of claim 21, further comprising releasing the medicaldevice from the body lumen after a period of 1-7 days.
 26. The method ofclaim 21, wherein determining whether the patient has experienced anevent includes determining whether the sensed direction of travel ofcontents is upstream.
 27. The method of claim 21, wherein the implantedmedical device includes a bioabsorbable portion.
 28. The method of claim21, wherein the implanted medical device is in the shape of a helix. 29.The method of claim 21, further comprising visualizing an area withinthe patient using an optical assembly of the implanted medical device.30. The method of claim 21, wherein the body lumen is the patient'sesophagus.
 31. A method for sensing within a body lumen of a patient,comprising: sensing a direction of travel of contents within the bodylumen with an impedance sensor of a medical device, wherein theimpedance sensor is exposed to an interior of the body lumen; based onthe sensed direction of travel, determining whether the patient hasexperienced an event; and transmitting data from the medical device to adata acquisition module located outside of a body of the patient when anupstream direction of travel is sensed.
 32. The method of claim 31,further comprising sensing a position of the patient with the implantedmedical device, and then determining whether a patient has experiencedthe event is further based on the sensed position.
 33. The method ofclaim 31, further comprising releasing the medical device from the bodylumen after 2-7 days.
 34. The method of claim 31, further comprisingwirelessly transmitting the sensed direction of travel to the dataacquisition module.
 35. The method of claim 31, wherein determiningwhether the patient has experienced an event includes sensing a pH withthe medical device and determining whether the sensed pH is less than 4for a period of 5 or more seconds.
 36. The method of claim 31, whereindetermining whether the patient has experienced an event includesdetermining whether the sensed direction of travel of contents isupstream.
 37. The method of claim 31, wherein the medical deviceincludes a bioabsorbable portion.
 38. The method of claim 31, whereinthe medical device is in the shape of a helix.
 39. The method of claim31, wherein the body lumen is the patient's esophagus.
 40. A method forsensing within a body lumen of a patient, comprising: sensing a pH withan implanted medical device coupled to the body lumen or sensing adirection of travel of contents within the body lumen with an impedancesensor of the medical device; based on the sensed pH or the senseddirection of travel, determining whether the patient has experienced anevent; transmitting data from the implanted medical device to a dataacquisition module located outside of a body of the patient; andreleasing the medical device from a wall of the body lumen viadeterioration of a bioabsorbable portion of the medical device.